Air ride seat question.

When parked and the brake is pulled I have a full hard seat, while moving the seat loses air.
I went out with the soap bottle a week or two ago and it seems like every plastic quick connect is leaking air. Is there a way to narrow it down to which one is the culprit?
Maybe be related I don't know, but the seat thing happens all the time, this other thing only once in a while. I will get a whistle under the hood. Right in front of the steering wheel. It never does it when parked so I can't identify what it is. My buddy thinks it where all the airlines hook up right in front. That piece he is thinking has kinda a rubber stopper on it. Atlease it does on his truck.
I can send a picture if need be. But that whistle is loud and comes out of no where. Runs its course then stops. I did rule out the turbo. Any help would be great thanks.

 

Ill post a picture Tommrow, thanks.

 

My buddy thinks its this